Prior art papers disclose laboratory experiments in microorganism biodegradation of toxic compounds, such as nitro-substituted DDT, by anaerobic treatment. Significant biodegradation of DDT occurred in these experiments, but toxic metabolites of DDT remained. Remediation, as hereinafter defined was not achieved by these prior art DDT techniques.
Recent U.S. Pat. Nos. 5,660,612 and 5,660,613 disclose the remediation of soil contaminated with DDT by a method comprising repeated cycles of anaerobic composting followed by aerobic composting under specific conditions of water content temperature, redox potential and the presence of microbes capable of transforming DDT into harmless materials.
We attempted to decontaminate soil containing various contaminants other than DDT. While this method has been found successful with a limited number of specific contaminants, it was unsuccessful for many contaminants, especially if one or more microbe inoculents are not added to the decontamination mixture. There was no reliable way to predict which compounds would be effectively decomposed by this method, and particularly no reason to expect that it would be successful in decontaminating soil containing no nitro-substituteded compounds. Conventional composting has also been tried, but anaerobic/aerobic sequence decontamination appears to be novel.
Experiments have been carried out biodegrading TNT by conventional anaerobic composting. As described in Crawford U.S. Pat. No. 5,455,173 experiments have been done to apply microbe degradation to soil contaminated with TNT and other explosives